1. Field of the Invention
The present invention relates to a droplet ejection head that ejects droplets to form an image on a recording paper sheet, a method of manufacturing a droplet ejection head, and a droplet ejection apparatus.
2. Description of the Related Art
The droplet ejection head (inkjet head) in a droplet ejection apparatus, such as an inkjet recording apparatus, that is used as an image recording apparatus or an image forming apparatus, such as a printer, a facsimile machine, or a copy machine, includes a nozzle to eject ink droplets; a pressure chamber (also referred to as an ink flow channel, a pressurizing liquid chamber, a pressurizing chamber, an ejection chamber, or a liquid chamber) communicating with the nozzle; and an electromechanical conversion element, such as an piezoelectric element, (or an electro-thermal conversion element, such as a heater) that applies pressure to the ink in the pressure chamber. In the droplet ejection head, a diaphragm is displaced using the energy generated by applying a voltage to the electromechanical conversion element to apply pressure to the ink in the pressure chamber so as to eject the ink droplets from the nozzle, thereby an image is formed on a recording paper sheet.
In such an inkjet recording apparatus, one or more inkjet heads to perform printing on a recording paper sheet are mounted on a carriage that is moved back and forth in a direction orthogonal to a direction in which the recording paper sheet is conveyed. The inkjet recording apparatus may have a configuration in which the inkjet head is attachable to and removable from the carriage. Making the inkjet head attachable to and removable from a given part of the carriage in the inkjet recording apparatus has advantages of reducing costs because it makes assembly easier during manufacturing and of improving appliance performance (ease of handling) when a user replaces the inkjet head.
In such an inkjet recording apparatus, in order to ensure the printing quality, i.e., in order to cause ink droplets to reach the recording paper sheet with high positioning accuracy, it is required to engage the inkjet head, including a base plate having a position reference surface that has improved accuracy, with a part of the inkjet recording apparatus at a given position. Furthermore, in accordance with a demand for a high image resolution in recent years, it is required to arrange nozzle holes and elements in a high density and it is also required to improve the accuracy of positioning the inkjet head with respect to the inkjet recording apparatus.
Thus, an inkjet recording head has been disclosed in which a position reference surface serving as a reference surface for a position at which the inkjet head is attached to the inkjet recording apparatus is formed of resin and the inkjet head is engaged with a part of the inkjet recording apparatus at a given position, thereby the accuracy of attaching the inkjet head to the inkjet recording apparatus is improved (see Japanese Patent No. 3495938).
Furthermore, an inkjet recording head has been disclosed in which a thermoplastic resin, such as poly phenylene sulfide (PPS) or poly phenylene ether (PPE) containing 80 wt % or more of fillers, is used as resin from which a support member having a position reference surface (reference surface) is formed, thereby the rigidity of the position reference surface is increased (see, Japanese Patent Application Laid-open No. 2010-280096).
Furthermore, a recording head cartridge incorporating an ink tank has been disclosed in which a base plate provided with a reference surface is formed of metal, such as aluminum, and the cartridge and the recording head are positioned only with respect to the base plate, whereby highly-accurate positioning can be performed (see, Japanese Patent No. 2698638).
However, when resin is used to form the position reference surface of the inkjet head as in the inkjet recording head of Japanese Patent No. 3495938, the position reference surface may deform due to insufficient rigidity or the size accuracy of the position reference surface may reduce by deformation of the position reference surface due to its insufficient rigidity or by the effect of thermal deformation of the member resulting from the change in environmental temperature due to the transport environment, etc., and accordingly the accuracy of positioning the inkjet head with respect to the inkjet recording apparatus may be reduced. This leads to a problem in that the accuracy with which ink droplets from the inkjet head reach the correct position on the recording paper sheet reduces, which reduces the image quality provided by the inkjet recording apparatus.
When a resin contains a large volume of fillers of 80 wt % as in the inkjet recording head of the Japanese Patent Application Laid-open No. 2010-280096, the manufacturing cost increases due to abrasion of a mold used in molding. There is also a problem in that the dust caused by the fillers and generated from the base plate reduces the ejection performance, which reduces the image quality.
When all position reference surfaces are provided only on a metallic base plate as in the recording head cartridge incorporating the ink tank, there is a problem in that, because the shape of the base plate is complicated, the accuracy of positioning the cartridge and the recording unit of the recording head with respect to each other is reduced and the cost of manufacturing increases.
There is a need to provide a droplet ejection head, a method of manufacturing a droplet ejection head, and a droplet ejection apparatus that improve the accuracy of positioning a droplet ejection head with respect to a droplet ejection apparatus when the droplet ejection head is attached to the droplet ejection apparatus, that improve the image quality, and that reduces the cost of manufacturing the droplet ejection head.